Show an interest in him. If you want to impress a guy, then you have to make him feel that you care about who he is as a person -- just not too much. When you do start talking to the guy, you should talk about the things he likes to do, what he's interested in, and just generally the things that intrigue him. This doesn't mean you should interview him or ask him too many questions, but it does mean that you should be attuned to the things he wants and cares about.